New protease inhibitors for HCV--help is on the way

Chronic hepatitis C: future treatment

The launch of first-generation protease inhibitors (PIs) is a major step forward in HCV treatment. However, the major advance is up to now restricted to genotype 1 (GT-1) patients. The development of second-wave and second-generation PIs yields higher antiviral potency through plurigenotypic activity, more convenient daily administration, fewer side effects and, for the second-generation PIs, potential activity against resistance-associated variants. NS5B inhibitors include nucleoside/nucleotide inhibitors (NIs) and non-nucleotide inhibitors (NNIs). NIs have high efficacy across all genotypes. Sofosbuvir has highly potent antiviral activity across all genotypes in association with pegylated interferon and ribavirin (PR), thus allowing shortened treatment duration. NS5A inhibitors (NS5A.I) have highly potent antiviral activity. It has recently been shown for the first time that NS5A.I in combination with protease inhibitors can cure GT-1b null responders in an interferon-free regimen. Besides, several studies demonstrate that interferon (IFN)-free regimens with direct-acting antiviral agent combinations are able to cure a large number of either naïve or treatment-experienced GT-1 patients. Moreover, quadruple regimen with PR is able to cure almost all GT-1 null responders. The development of pan-genotypic direct-acting antiviral agents (NIs or NS5A.I) allows new combinations with or without PR that increase the rate of sustained virological response for all patients, even for those with cirrhosis and independently of the genotype. Therefore, the near future of HCV treatment looks promising. The purpose of this article is to provide an overview of the clinical results recently reported for HCV treatment.

An update on the treatment of genotype-1 chronic hepatitis C infection: lessons from recent clinical trials

The launch of first-generation protease inhibitors (PIs) was a major step forward in hepatitis C virus (HCV) treatment. However, this major advance is, up to now, restricted to genotype-1 (GT-1) patients. However, the ongoing development of new direct-acting antiviral agents (DAAs) allows new hope for the future. The development of second-wave and second-generation PIs yields higher antiviral potency through plurigenotypic activity, more convenient daily administration, fewer side effects and, for the second-generation PIs, potential activity against resistance-associated variants. NS5B inhibitors (NS5B.I) include nucleoside/nucleotide inhibitors (NIs) and nonnucleotide inhibitors (NNIs). NIs have high efficacy across all genotypes. Sofosbuvir has highly potent antiviral activity across all genotypes in association with pegylated interferon (IFN) and ribavirin (PR), thus allowing shortened treatment duration. NS5A inhibitors (NS5A.I) have highly potent antiviral activity. It has recently been shown for the first time that NS5A.I in combination with PI can cure GT-1b null-responder patients in an IFN-free regimen. In addition, several studies demonstrate that IFN-free regimens with DAA combinations are able to cure a large number of either naïve or treatment-experienced GT-1 patients. Moreover, a quadruple regimen with PR is able to cure almost all GT-1 null-responders. The development of pan-genotypic DAAs (NIs or NS5A.I) allows new combinations with or without PR that increase the rate of sustained virological response (SVR) for all patients, even for those with cirrhosis and independently of the genotype. Therefore, the near future of HCV treatment looks promising. The purpose of this article is to provide an overview of the clinical results recently reported for HCV treatment in GT-1 patients.

How to optimize HCV therapy in genotype 1 patients with cirrhosis

Of all hepatitis C virus patients, those with cirrhosis are most in need of treatment owing to increased morbidity and mortality. Treatment with pegylated interferon and ribavirin (PEG-IFN/RBV) has clearly shown the benefits of successful treatment by improving fibrosis, causing the regression of cirrhosis and reducing and preventing cirrhosis-related complications. However, the sustained virological response (SVR) is lower in patients with cirrhosis. First generation protease inhibitors (boceprevir and telaprevir) in combination with PEG-IFN/RBV are a major advancement in the treatment of both naïve and treatment-experienced genotype 1 patients. In naïve patients, the SVR rate with the triple regimen with boceprevir increased by 14% in patients with severe fibrosis or cirrhosis compared to PEG-IFN/RBV compared by 30% in patients with mild or moderate fibrosis. The SVR rate of the triple regimen with telaprevir increased by 10-30% compared to PEG-IFN/RBV in patients with severe fibrosis or cirrhosis and by nearly 30% in patients with mild or moderate fibrosis. The greatest benefits seem to be found in patients with cirrhosis who have relapsed, and is limited in prior non-responder patients. Thus, the choice of triple therapy in the latter should be considered in relation to the increase in side effects. There are no data on the efficacy of the triple regimen in patients with decompensated cirrhosis. Results in real-life settings show that patients with cirrhosis need to be carefully followed-up during treatment due to the increase in side effects that are greater than in clinical studies. Next generation DAAs and PEG-IFN/RBV appear to be more effective and have fewer side effects in patients with cirrhosis. Ultimately, an interferon-free regimen of DAAs combinations will probably provide a SVR in patients with cirrhosis and will probably be proposed in patients with more advanced or decompensated cirrhosis.

Chronic hepatitis C: treatments of the future

The launch of first-generation protease inhibitors (PIs) was a major step forward in hepatitis C virus (HCV) treatment. However, this major advance has, up to now, only been applicable to genotype-1 patients. Second-wave and second-generation PIs appear to achieve higher antiviral potency, with pan-genotype activities, fewer side-effects and potential activity against PI-resistant mutation by second-generation PIs, through more convenient daily administration. Other direct-acting antivirals (DAAs) include NS5B inhibitors such as nucleoside/nucleotide inhibitors (NIs) and non-nucleoside inhibitors (NNIs). NIs have similar efficacy across all genotypes and present with the highest barrier to resistance of all DAAs to date. PSI-7977, a pyrimidine nucleotide analogue, also has highly potent antiviral activity across all HCV genotypes. In combination with ribavirin in an interferon-free regimen, it can achieve a 100% sustained viral response (SVR) rate in genotype 2/3 treatment-naïve patients. In association with pegylated interferon and ribavirin (PR), it achieves an SVR of 91% in genotype-1 naïve patients. NNIs in association with PR appear to be less potent, but they may nonetheless play a key role in many of the combination trials including either PIs or NIs. NS5A inhibitors also exhibit highly potent antiviral activity. Evaluation of their activity in combination with PIs demonstrated for the first time that an interferon-free regimen can cure genotype-1b null-responder patients. Furthermore, quadruple therapy with PR can achieve a 100% SVR in genotype-1 null-responder patients. Other players in the field, such as cyclophilin inhibitors and therapeutic vaccines, may have a role in combination with DAAs. The near future of HCV treatment looks promising. However, whether or not DAA combinations will lead to an interferon-free regimen for all patients remains an open question.

Second-wave protease inhibitors: choosing an heir

Infection with the hepatitis C virus (HCV) is a major cause of chronic liver disease and a leading indication of liver transplantations worldwide. The current standard of care for chronic hepatitis C is a combination of pegylated interferon-α and ribavirin that is effective in slightly more than half of cases and is associated with significant side effects. The first directly acting antivirals recently reached the US market, but will have shortcomings that should in part be overcome by the second-wave PIs that are in development. This article gives an overview of the compounds that will soon be available.